Peripheral venous pressure is an alternative to central venous pressure in paediatric surgery patients

BACKGROUND: Peripheral venous pressure (PVP) is easily and safely measured. In adults, PVP correlates closely with central venous pressure (CVP) during major non-cardiac surgery. The objective of this study was to evaluate the agreement between CVP and PVP in children during major surgery and during recovery. METHODS: Fifty patients aged 3-9 years, scheduled for major elective surgery, each underwent simultaneous measurements of CVP and PVP at random points during controlled ventilation intraoperatively (six readings) and during spontaneous ventilation in the post-anaesthesia care unit (three readings). In a subset of four patients, measurements were taken during periods of hypotension and subsequent fluid resuscitation (15 readings from each patient). RESULTS: Peripheral venous pressure was closely correlated to CVP intraoperatively, during controlled ventilation (r=0.93), with a bias of 1.92 (0.47) mmHg (95% confidence interval = 2.16-1.68). In the post-anaesthesia care unit, during spontaneous ventilation, PVP correlated strongly with CVP (r = 0.89), with a bias of 2.45 (0.57) mmHg (95% confidence interval = 2.73-2.17). During periods of intraoperative hypotension and fluid resuscitation, within-patient changes in PVP mirrored changes in CVP (r = 0.92). CONCLUSION: In children undergoing major surgery, PVP showed good agreement with CVP in the perioperative period. As changes in PVP parallel, in direction, changes in CVP, PVP monitoring may offer an alternative to direct CVP measurement for perioperative estimation of volume status and guiding fluid therapy.     

Peripheral venous pressure as a predictor of central venous pressure during orthotopic liver transplantation

STUDY OBJECTIVE: To assess the reliability of peripheral venous pressure (PVP) as a predictor of central venous pressure (CVP) in the setting of rapidly fluctuating hemodynamics during orthotopic liver transplant surgery. DESIGN: Prospective clinical trial. SETTING: UCLA Medical Center, main operating room-liver transplant surgery. PATIENTS: Nine adult patients with liver failure undergoing orthotopic liver transplant surgery. INTERVENTIONS: A pulmonary artery catheter and a 20-g antecubital peripheral intravenous catheter dedicated to measuring PVP were placed in all patients after standard general endotracheal anesthesia induction and institution of mechanical ventilation. MEASUREMENTS: Peripheral venous pressure and CVP were recorded every 5 minutes and/or during predetermined, well-defined surgical events (skin incision, venovenous bypass initiation, portal vein anastamosis, 5 minute post graft reperfusion, abdominal closure). Pulmonary artery pressure and cardiac output (via thermodilution) were recorded every 15 and 30 minutes, respectively. MAIN RESULTS: Peripheral venous pressure (mean +/- SD) was 11.0 +/- 4.5 mmHg vs a CVP of 9.5 +/- 5.0; the two measurements differed by an average of 1.5 +/- 1.6 mmHg. Peripheral venous pressure correlated highly with CVP in every patient, and the overall correlation among all nine patients calculated using a random-effects regression model was r = 0.95 (P < 0.0001). A Bland-Altman analysis used to determine the accuracy of PVP in comparison to CVP yielded a bias of -1.5 mmHg and a precision of +/-3.1 mm Hg. CONCLUSION: Our study confirms that PVP correlates with CVP even under adverse hemodynamic conditions in patients undergoing liver transplantation.     

Correlation of peripheral venous pressure and central venous pressure in surgical patients

OBJECTIVE: To determine the degree of agreement between central venous pressure (CVP) and peripheral venous pressure (PVP) in surgical patients. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Patients without cardiac dysfunction undergoing major elective noncardiac surgery (n = 150). MEASUREMENTS AND MAIN RESULTS: Simultaneous CVP and PVP measurements were obtained at random points in mechanically ventilated patients during surgery (n = 100) and in spontaneously ventilating patients in the postanesthesia care unit (n = 50). In a subset of 10 intraoperative patients, measurements were made before and after a 2-L fluid challenge. During surgery, PVP correlated highly to CVP (r = 0.86), and the bias (mean difference between CVP and PVP) was -1.6 +/- 1.7 mmHg (mean +/- SD). In the postanesthesia care unit, PVP also correlated highly to CVP (r = 0.88), and the bias was -2.2 +/- 1.9 (mean +/- SD). When adjusted by the average bias of -2, PVP predicted the observed CVP to within +/-3 mmHg in both populations of patients with 95% probability. In patients receiving a fluid challenge, PVP and CVP increased similarly from 6 +/- 2 to 11 +/- 2 mmHg and 4 +/- 2 to 9 +/- 2 mmHg. CONCLUSION: Under the conditions of this study, PVP showed a consistent and high degree of agreement with CVP in the perioperative period in patients without significant cardiac dysfunction. PVP -2 was useful in predicting CVP over common clinical ranges of CVP. PVP is a rapid noninvasive tool to estimate volume status in surgical patients.     

Effect of catheter site on the agreement of peripheral and central venous pressure measurements in neurosurgical patients

STUDY OBJECTIVE: Previous studies suggest a correlation of central venous pressure (CVP) with peripheral venous pressure (PVP) in different clinical setups. The aim of this study was to investigate the effect of measurement site on PVP and its agreement with CVP in patients undergoing general anesthesia. DESIGN: Prospective randomized study. SETTINGS: University hospital. PATIENTS: Thirty patients of American Society of Anesthesiologists physical status I and II undergoing elective craniotomy. INTERVENTIONS: Patients were randomly assigned into Group A (antecubital; n=15) and Group D (dorsum hand; n=15) for antecubital and hand dorsum catheterization sites, respectively. Central venous pressure and PVP were monitored throughout the study. A total of 1925 simultaneous measurements were recorded at 5-minute intervals. Bland-Altman assessment for agreement was used for CVP and PVP in 2 groups. MEASUREMENTS: Peripheral venous pressure measurements were within the range of +/-2 mm Hg of CVP values, in 93.9% of the measurements in Group A, and in 91.2% of the measurements in Group D. Considering all measurements, mean bias was -0.072 mm Hg (95% CI, -0.134 to -0.010). Group A measurements showed a bias (CVP-PVP) of 0.173+/-3.557 mm Hg, whereas the bias was -0.122+/-4.322 mm Hg (mean+/-SDcorrected for repeated measurements) in Group D. All of the measurements were within mean+/-2SD of bias, which means that PVP and CVP are interchangeable in our clinical setting. CONCLUSION: Peripheral venous pressure measurement may be a noninvasive alternative for estimating CVP in patients undergoing elective neurosurgical operations. Measuring PVP from hand dorsum does not interfere with the agreement of CVP and PVP.     

Correlation of peripheral venous pressure and central venous pressure in kidney recipients

BACKGROUND AND OBJECTIVE: Previous studies in adults have demonstrated a clinically useful correlation between central venous pressure (CVP) and peripheral venous pressure (PVP). The current study prospectively compared CVP measurements from a central versus a peripheral catheter in kidney recipients during renal transplantation. METHODS: With ethics committee approval and informed consent, 30 consecutive kidney recipients were included in the study. We excluded patients who had significant valvular disease or clinically apparent left ventricular failure. For each of 30 patients, CVP and PVP were measured on five different occasions. The pressure tubing of the transducer system was connected to the distal lumen of the central or to the peripheral venous catheter for measurements following induction of anesthesia, after induction, 1 hour after induction, reperfusion of the kidney, and the end of the operation, yielding 150 hemodynamic data points. Each hemodynamic measurement included heart rate, mean arterial pressure, mean CVP, and mean PVP determined at end-expiration. RESULTS: The mean PVP was 13.5 +/- 1.8 mm Hg and the mean CVP was 11.0 +/- 1.5 mm Hg during surgery. The mean difference was 2.5 +/- 0.5 (P < .01). Repeated-measures analysis of variance indicated a highly significant relationship between PVP and CVP (P < .01) with a Pearson correlation coefficient of 0.97. CONCLUSION: Under the conditions of this study, PVP showed a consistently high agreement with CVP in the perioperative period among patients without significant cardiac dysfunction.     

Effect of body temperature on peripheral venous pressure measurements and its agreement with central venous pressure in neurosurgical patients

Previous studies suggest a correlation of central venous pressure (CVP) with peripheral venous pressure (PVP) in different clinical settings. The effect of body temperature on PVP and its agreement with CVP in patients under general anesthesia are investigated in this study. Fifteen American Society of Anesthesiologists I-II patients undergoing elective craniotomy were included in the study. CVP, PVP, and core (Tc) and peripheral (Tp) temperatures were monitored throughout the study. A total of 950 simultaneous measurements of CVP, PVP, Tc, and Tp from 15 subjects were recorded at 5-minute intervals. The measurements were divided into low- and high-Tc and -Tp groups by medians as cutoff points. Bland-Altman assessment for agreement was used for CVP and PVP in all groups. PVP measurements were within range of +/-2 mm Hg of CVP values in 94% of the measurements. Considering all measurements, mean bias was 0.064 mm Hg (95% confidence interval -0.018-0.146). Corrected bias for repeated measurements was 0.173 +/- 3.567 mm Hg (mean +/- SD(corrected)). All of the measurements were within mean +/- 2 SD of bias, which means that PVP and CVP are interchangeable in our setting. As all the measurements were within 1 SD of bias when Tc was > or = 35.8 degrees C, even a better agreement of PVP and CVP was evident. The effect of peripheral hypothermia was not as prominent as core hypothermia. PVP measurement may be a noninvasive alternative for estimating CVP. Body temperature affects the agreement of CVP and PVP, which deteriorates at lower temperatures.     

Hemodynamic monitoring

The goal of hemodynamic monitoring is to maintain adequate tissue perfusion. Classical hemodynamic monitoring is based on the invasive measurement of systemic, pulmonary arterial and venous pressures, and of cardiac output. Since organ blood flow cannot be directly measured in clinical practice, arterial blood pressure is used, despite limitations, as estimate of adequacy of tissue perfusion. A mean arterial pressure (MAP) of 70 mm Hg may be considered a reasonable target, associated with sign of adequate organ perfusion, in most patients. In the approach to hypotension, which is the most common cause of hemodynamic instability in critical ill patients, increasing levels of monitoring may be used. Assuming that central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) are adequate estimates of the volume of the systemic and pulmonary circulation respectively, the following decision tree is suggested: 1) make a working diagnosis based on the relationship between pressure (CVP and PAOP) and cardiac output or stroke volume (CO or SV); 2) consider conditions that may alter reliability of CVP and PAOP in estimate adequately circulating volumes such as abnormal pressure/volume relationship (compliance) of the RV or LV, increased intrathoracic pressure (PEEP, autoPEEP, intra-abdominal pressure), valvular heart disease (mitral stenosis); 3) look at the history; 4) separating RV and LV by reciprocal variations of CVP, PAOP and SV. CVP is often used as sole parameter to monitor hemodynamic. However CVP alone may not differentiate between changes in volume (different venous return curve) or changes in contractility (different starling curve). Finally, other techniques such as echocardiography, transesophageal Doppler and volume-based monitoring system are now available.     

Comparative utility of centrally versus peripherally transduced venous pressure monitoring in the perioperative period in spine surgery patients

Study ObjectiveTo compare central venous pressure (CVP) with peripheral venous pressure (PVP) monitoring during the intraoperative and postoperative periods in patients undergoing spine surgery.DesignProspective observational study.SettingUniversity-affiliated teaching hospital.Patients35 ASA physical status 1, 2, and 3 patients.InterventionsA peripheral catheter in the forearm or hand and a central catheter into the internal jugular vein were placed for PVP and CVP monitoring, respectively.MeasurementsCVP and PVP values were collected simultaneously and recorded electronically at 5-minute intervals throughout surgery and in the recovery room. The number of attempts for catheter placement, ease of use, maintenance, and interpretation were recorded. Patient comfort, frequency of complications, and cost were analyzed.Main resultsThe correlation coefficient between CVP and PVP was 0.650 in the operating room (P < 0.0001) and 0.388 in the recovery room (P < 0.0001). There was no difference between groups in number of attempts to place either catheter, maintenance, and interpretation with respect to PVP and CVP monitoring in the operating room. In the recovery room, the nurses reported a higher level of difficulty in interpretation of PVP than CVP, but no differences were noted in ease of maintenance. There were no complications related to either central or peripheral catheter placement. Patient comfort and cost efficiency were higher with a peripheral than a central catheter.ConclusionDuring clinically relevant conditions, there was limited correlation between PVP and CVP in the prone position during surgery and postoperatively in the recovery room.     

Peripheral venous pressure as a measure of venous compliance during pheochromocytoma resection

Venous pressures measured from peripheral venous catheters (PVP) closely estimate the central venous pressure (CVP) in surgical and critically ill patients. CVP is often used to estimate intravascular volume; however, fluctuations of CVP may also be induced by changes in venous tone caused by alpha-adrenergic catecholamine stimulation. We simultaneously monitored PVP, CVP, and mean arterial blood pressure during resection of pheochromocytoma in a 63-yr-old woman and found excellent correlation between the three pressure variables, suggesting that fluctuations of PVP reflect overall changes in vascular tone.     

Usefulness of a central venous catheter during hepatic surgery

Aim: Central venous catheter (CVC) is often inserted during liver resection because a low central venous pressure (CVP) reduces blood loss and the procedure may be associated with circulatory impairment. The aim of the study was to evaluate the usefulness of a CVC besides the measurements of CVP, and whether peripheral venous pressure (PVP) measurement could be used reliably in place of CVP.
Methods: We conducted an observational study during a 16-month period. Number of CVC inserted, expected surgical difficulties, and intraoperative complications which could lead to treatment involving a CVC were prospectively recorded and analysed. Measurements of CVP and PVP were simultaneously obtained at different times during surgery. Bias and limits of agreement with their 95% confidence interval (95% CI) were calculated.
Results: Of the 101 patients included, 28 had expected surgical difficulties. Of the 75 CVCs inserted, only six (8%) were used for another purpose that CVP measurement in patients with expected surgical difficulties. A total of 124 measurements in 23 patients were recorded. Mean CVP was 4.8 ± 2.9 mmHg and mean PVP was 6.9 ± 3.1 mmHg ( P <0.0001). The bias was −2.1 ± 1.1 mmHg (95% CI: −2.3 to −1.9). When adjusted by the average bias of −2 mmHg, PVP predicted a CVP≤5 mmHg with a sensitivity and a specificity of 93% and 87%, respectively.
Conclusion: Routine insertion of a CVC should be discussed in patients without expected surgical difficulties. Thus, PVP monitoring may suffice to estimate CVP in uncomplicated cases.     

Hemodynamic effects of intraaortic versus intravenous protamine administration after cardiopulmonary bypass in man.

A hemodynamic study of men undergoing elective coronary artery bypass surgery was undertaken to elucidate the side effects of protamine given into the ascending aorta (group A, n = 16) or into the central venous line (group V, n = 16). After termination of extracorporeal circulation, protamine was infused over 120 seconds, and the hemodynamic profile was continuously recorded. During the first minute, the systemic arterial pressure fell to about 60% of the preprotamine level in both groups, but the hemodynamic changes occurred more rapidly (p < 0.05) in group V than in group A, with maximal pressure drop at 61.7 +/- 2.7 vs 74.4 +/- 4.9 seconds. Following spontaneous restoration of the systemic blood pressure, the pulmonary artery pressure rose considerably in both groups, as did the pulmonary capillary wedge and central venous pressures, reaching higher levels in the intravenous group. The cardiovascular responses were again more rapid in group V than in group A (p = 0.004). The degree of systemic hypotension thus did not benefit from use of the intraaortic rather than the intravenous route for administering protamine. The more pronounced and more rapid pulmonary circulatory changes in the intravenous group suggest that the hemodynamic effects of protamine are initiated in the lungs.     

Peripheral venous pressure predicts central venous pressure poorly in pediatric patients

Purpose: Using peripheral venous pressure (PVP) instead of central venous pressure (CVP) as a volume monitor decreases patient risks and costs, and is convenient. This study was undertaken to determine if PVP predicts CVP in pediatric patients. METHODS: With ethical approval and informed consent, 30 pediatric patients aged neonate to 12 yr requiring a central venous line were studied prospectively in a tertiary care teaching hospital. In the supine position, PVP and CVP were simultaneously transduced. Ninety-six paired recordings of CVP and PVP were made. Correlation and Bland-Altman analysis of agreement of end-expiratory measurements were performed. RESULTS: The mean (SD; range) CVP was 10.0 mmHg (6.0; -1.0 to 27.0); the mean PVP was 13.7 mmHg (6.3; 0.0 to 33.0); offset (bias) of PVP > CVP was 3.7 mmHg with SD 2.6. The 95% confidence intervals (CI) for the bias were 3.2 to 4.1 mmHg. In the Bland-Altman analysis, lower and upper limits of agreement (LOA; CI in parentheses) were -1.5 (-2.3 to -0.7) and 8.8 (8.1 to 9.6) mmHg. Eight of 96 points were outside the limits of agreement. The correlation of PVP on CVP was r = 0.92, P < 0.0001. For a subset of ten patients (20 simultaneous recordings) with iv catheters proximal to the hand, limits of agreement were better - offset: 3.8 mmHg (+/- 1.4); lower LOA: 1.2 mmHg (0.25 to 2.1); upper LOA: 6.6 mmHg (5.7 to 7.5). CONCLUSION: Peripheral venous pressure measured from an iv catheter in the hand predicts CVP poorly in pediatric patients.     

Effects of initiation of continuous renal replacement therapy on hemodynamics in a pediatric animal model

There are no studies analyzing the initial hemodynamic impact of continuous renal replacement therapy (CRRT) in children. We have performed a prospective observational study in 34 immature Maryland pigs to analyze the initial hemodynamic changes during venovenous CRRT. The heart rate, blood pressure, central venous pressure (CVP), pulmonary arterial occlusion pressure (PAOP), pulmonary capillary wedge pressure, temperature, and cardiac output (CO), simultaneously by pulmonary arterial thermodilution and femoral arterial thermodilution, were measured at 30-min intervals during 2 h. Venovenous CRRT induced an initial significant diminution of volemic hemodynamic parameters (intrathoracic blood volume, global end-diastolic volume, stroke volume index, PAOP, and CVP). Simultaneously, a significant increase in systemic vascular resistance index and left ventricular contractility, and a decrease in CO, was observed. We conclude that CRRT in a pediatric animal model induces initial hypovolemia, and a systemic cardiovascular response with vasoconstriction and increase in ventricular contractility.     

Effects of Initiation of Continuous Renal Replacement Therapy on Hemodynamics in a Pediatric Animal Model

There are no studies analyzing the initial hemodynamic impact of continuous renal replacement therapy (CRRT) in children. We have performed a prospective observational study in 34 immature Maryland pigs to analyze the initial hemodynamic changes during venovenous CRRT. The heart rate, blood pressure, central venous pressure (CVP), pulmonary arterial occlusion pressure (PAOP), pulmonary capillary wedge pressure, temperature, and cardiac output (CO), simultaneously by pulmonary arterial thermodilution and femoral arterial thermodilution, were measured at 30-min intervals during 2 h. Venovenous CRRT induced an initial significant diminution of volemic hemodynamic parameters (intrathoracic blood volume, global end-diastolic volume, stroke volume index, PAOP, and CVP). Simultaneously, a significant increase in systemic vascular resistance index and left ventricular contractility, and a decrease in CO, was observed. We conclude that CRRT in a pediatric animal model induces initial hypovolemia, and a systemic cardiovascular response with vasoconstriction and increase in ventricular contractility.     

Role of the venous system in hemodynamics during ultrafiltration and bicarbonate dialysis.

A reduced venous compliance (VC) and inadequate venoconstriction may impair hemodynamics during hemodialysis, the first by impairing plasma volume preservation and by inducing a steep fall in central venous pressure (CVP) during minor plasma volume loss, the second by inadequate mobilization of hemodynamically inactive blood volume. For the protocol A, the relation between VC, the fall in plasma volume and the decline in central venous pressure (CVP) was assessed in 12 hemodialysis (HD) patients, aged 40 to 74 years, during isolated ultrafiltration (UF). The patients were ultrafiltrated for one hour at an UF rate of 1 to 1.5 liter/hr. VC was measured by strain gauge plethysmography with direct i.v. pressure measurements. CVP was assessed directly via a subclavian catheter. PVP was measured using the serial hematocrit method. VC correlated inversely with the fall in plasma volume (r = -0.66; P less than 0.025) and with the fall in CVP (corrected for UF volume) (r = -0.62; P less than 0.025). In the protocol B, the constriction of veins and resistance vessels was assessed sequentially during isolated UF and during UF combined with bicarbonate HD (UF + HD) by measuring the change in venous tone (VT) and vascular resistance (FVR) of the forearm. Twelve HD patients were studied (age 30 to 64 years). VT and FVR were measured using strain gauge plethysmography. The UF rate was equal during isolated UF and UF + HD (1 liter/hr). In six patients, the measurements were started with isolated UF and in six patients with UF + HD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of intrathoracic blood volume as an indicator of cardiac preload: single transpulmonary thermodilution technique versus assessment of pressure preload parameters derived from a pulmonary artery catheter.

OBJECTIVE: To analyze the clinical value of a new device (PiCCO) for cardiac output measurement and volume preload parameter assessment, based on transpulmonary thermodilution technique, as an alternative to the pulmonary artery thermodilution technique and assessment of pressure preload parameters derived from the pulmonary artery catheter. DESIGN: Prospective, controlled, clinical study. SETTING: University hospital. PARTICIPANTS: Eighteen patients with ejection fraction >50% undergoing coronary artery bypass graft surgery. INTERVENTIONS: A baseline measurement was performed after induction of anesthesia under clinical steady-state conditions (T1). Hypovolemia, defined as central venous pressure (CVP) <10 mmHg and pulmonary capillary wedge pressure (PCWP) <12 mmHg, was treated by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL/kg). After 10 minutes, a second measurement (T2) was performed. MEASUREMENTS AND MAIN RESULTS: The mean difference (bias) between transpulmonary thermodilution cardiac output and pulmonary artery thermodilution cardiac output did not differ at the 2 sample points. Changes in pressure preload parameters of the pulmonary artery catheter (CVP, PCWP) did not correlate with changes in cardiac output or stroke volume, whereas changes in volume preload parameter intrathoracic blood volume (ITBV) of the PiCCO correlated significantly with changes in cardiac output and stroke volume (r = 0.55, p < 0.05; r = 0.62, p < 0.01). CONCLUSION: These results suggest that increased cardiac preload is more reliably reflected by ITBV than by CVP or PCWP. The assessment of ITBV by the transpulmonary single indicator dilution technique is an interesting alternative to the pressure preload parameters.     

Can peripheral venous pressure be an alternative to central venous pressure during right hepatectomy in living donors?

The safety of living donors is a matter of cardinal importance in addition to obtaining optimal liver grafts to be transplanted. Central venous pressure (CVP) is known to have significant correlation with the amount of bleeding during parenchymal transection and many centers have adopted CVP monitoring for right hepatectomy. However, central line cannulation can induce some serious complications. Peripheral venous pressure (PVP) has been suggested as a comparable alternative to CVP. The aim of this study was to determine whether a clinically acceptable agreement or a reliable correlation between CVP and PVP exist and if CVP can be replaced by PVP in living liver donors. A central venous catheter was placed through the right internal jugular vein and a peripheral venous catheter was inserted at antecubital fossa in the right arm. CVP and PVP were recorded in 15-minute intervals in 50 adult living donors. The paired data were divided into 3 stages: preparenchymal transection, parenchymal transection, and postparenchymal transection. A total of 1,430 simultaneous measurements of CVP and PVP were recorded. Overall, the PVP, CVP, and bias were 7.0+/-2.46, 5.9+/-2.32, and 1.16+/-1.12 mmHg, respectively. A total of 88.9% of all measurements were clinically within acceptable limits of bias (+/-2 mmHg). Regression analysis showed a high correlation coefficient between PVP and CVP (r=0.893; P<0.001) and the limits of agreement were -1.03 to 3.34 overall. In conclusion, frequencies of differences, bias, correlation coefficient, and limits of agreement between PVP and CVP remained relatively constant throughout the operation. Therefore, PVP measurement in the arm can be an alternative to predict CVP and further, obviate central venous catheter-related complications in living liver donors.     

经食管超声多普勒在部分肝切除术液体治疗中的应用

目的研究经食管超声多普勒血液动力学监测对部分肝切除术中液体治疗的指导价值。方法将40例拟行部分肝切除术的患者随机均分为经食管超声多普勒组(D组)和中心静脉压(CVP)组(C组)。D组采用经食管超声多普勒进行血液动力学监测指导术中输液,C组采用CVP监测指导术中输液,观察两组患者输液量、血液动力学变化和液体治疗的效果。结果D组较C组患者血液动力学稳定。结论经食管超声多普勒可以动态瞬时监测患者的血液动力学,全面了解患者的心脏功能和循环状况,是一种指导大手术中液体治疗的有效的无创监测手段。     

Volumenstatus und zentraler Venendruck

Values of intramural or even transmural central venous pressure (CVP) as well as values of pulmonary artery occluded pressure do not correlate with the values of measured circulating blood volume or with responsiveness to fluid challenge. The veins contain approximately 70% of the total blood volume and are 30 times more compliant than arteries, therefore, changes in blood volume within the veins are associated with relatively small changes in venous pressure. The main reason for a lack of correlation between CVP values and blood volume is that the body does everything possible to maintain homeostasis and adequate transmural CVP is a must for cardiovascular function. The most accurate measurement of volume status would be the mean circulatory filling pressure (MCFP), which cannot be measured in a clinical setting. Stressed volume determines MCFP and directly affects venous return and cardiac output whereas unstressed volume is a reserve of blood that can be mobilized into circulation when needed. Both stressed and unstressed volume cannot be adequately measured. Therefore, considering the complexity of the physiologic feedback and clinical picture, robust reflexes and homeostatic mechanisms, CVP is insufficient as a surrogate parameter for assessing the volume status.     

The effect of the prone position on venous pressure and blood loss during lumbar laminectomy.

STUDY OBJECTIVE: To determine the effects of three different prone support systems (Andrews spinal surgery frame, Cloward surgical saddle, and longitudinal bolsters) on inferior vena cava (IVC) and superior vena cava (SVC) pressures; the validity of measuring central venous pressure (CVP) for the determination of ideal positioning of the patient; and the relationship among frame type, blood loss, and hemodynamic measurements. DESIGN: Prospective, randomized study of the hemodynamic effects of the prone position. SETTING: Inpatient surgery at a university hospital (regional spinal cord injury treatment center). PATIENTS: Eighteen patients free of significant coexisting disease (ASA physical status I and II) undergoing elective lumbar laminectomy. INTERVENTIONS: Patients were assigned to one of three support frames and measurement of SVC pressure, IVC pressure, and mean arterial pressures (MAP) were obtained supine, prone, and after repositioning. These pressures and measured blood loss were obtained every 15 minutes during the surgical laminectomy portion of the procedure. MEASUREMENTS AND MAIN RESULTS: Patients positioned on the Andrews frame had decreased mean SVC and IVC pressures from 8.7 mmHg and 8.4 mmHg in the supine position to 3.3 mmHg and 1.8 mmHg in the prone position, respectively (p less than 0.001). Prone position CVP also was significantly lower in the Andrews group compared with that in the other two groups (p less than 0.001). Repositioning efforts did not significantly decrease CVP. Blood loss was higher in the Cloward group (1,150 +/- 989 ml) than in the Andrews (245 +/- 283 ml) and bolsters (262 +/- 188 ml) groups (p less than 0.02). CONCLUSIONS: Increased blood loss was not associated with increased SVC or IVC pressure, nor was there any significant correlation between any demographic or hemodynamic variable and blood loss. There was no evidence that CVP is useful in determining the ideal prone position in patients undergoing lumbar laminectomy.